(1) Field of the Invention
This invention relates to a multiple-processor information processing system, and more particularly to a multiple-processor information processing system having a plurality of processor modules.
(2) Description of the Related Art
Conventionally, an information processing system having a plurality of processor modules (PMs) (hereinafter referred to as “the multiple-processor information processing system”) carries out TCP/IP (Transmission Control Protocol/Internet Protocol) communication by two methods; a method of using a real IP address, and a method of employing a virtual IP address.
Here, the term “real IP address” is used to mean an IP address which corresponds to a communication medium of each PM, and is set on a PM-by-PM basis and on a communication medium-by-communication medium basis. On the other hand, the term “virtual IP address” is used to mean an IP address which the system can have independently of the PMs and the communication media, and appears to an adjacent IP router and a communication opposite party as if it were an address of a remote network/host system which exists beyond the real IP address which the multiple-processor information processing system has.
The use of a virtual IP address as described above enables the communication opposite party to carry out the TCP/IP communication without being conscious of the configuration of the PMs of the system and their communication media.
In the TCP/IP communication, since a virtual IP address appears to be an address of a remote network/host system, routing information can be transmitted to the adjacent IP router by using a RIP (Routing Information Protocol).
However, in the conventional multiple-processor information processing system, only one virtual IP address is assigned to all the PMs, so that when communication is carried out by using the virtual IP address, all the communication processes are allocated to all the PMs such that the number of connections is made uniform among the PMs, thereby balancing the load across the PMs. As a result, different communication processes can be assigned to one PM, and if a certain communication process is overloaded, it adversely affects the other communication processes.
Further, due to the increasingly widespread use of the Internet in recent years, such a system can sometimes experience concentrated access from a large indefinite number of users during a particular time of the day. If the system uses a virtual IP address in such a case, the processing load on all the PMs is temporarily increased, thereby suppressing execution of particular services necessitating prompt processing, causing the trouble in providing the services.